=Testing fuses.=—The following apparatus is used for testing in the loading room: A double-pole double-throw switch, a 150-volt voltmeter, and sufficient dry cells to give a full throw when using the lower scale of the voltmeter. The apparatus is connected up on the testing table so as to make resistance measurements by the voltmeter method. To test fuses, leads are carried from the switch to an iron or other suitable receptacle outside of the building and the fuse leads joined thereto. A full deflection should be obtained when the circuit is closed through the fuses. =Preparing a compound plug for service.=—The transformer to be used is first tested for a good circuit between the red wires, a poor circuit between the ends of the black wire, a good circuit between the black or primary lead and the reactance terminal, no circuit between the red and black wires, and no circuit between any wire and the case. The resistance of the circuits is determined by the voltmeter method. The upper end of the black wire (see fig. 8) is prepared for use by baring the wire for about one-half inch and securing it to the binding post in the neck of the transformer. The ball seat is screwed home. The spring plate, distance ring, and ball are placed in the circuit-closer cap, which is held inverted and the transformer screwed into it, the threads being coated with ruberine. (_a_) =Old model, brass fuse can.=—Starting with the compound plug dismantled. A piece of loading wire is cut about 3 feet long and the ends bared. One end is joined by a telegraph joint to the primary terminal of the transformer and the joint is taped. This wire and the two secondary wires are drawn through the fuse can, which is screwed on the transformer, the threads of the latter having first been coated with ruberine. Two mine service fuses, which have been tested for continuity of circuit, are connected in multiple across the secondary (red) terminals and the joints taped. The can is held vertically and the explosive, if trotol, poured in up to the screw threads for the fuse can cap; if dynamite, inclosed in a cloth bag and placed in the can. The fuses are embedded in the explosive. The loading wire is drawn through a lead washer and the fuse can cap; the latter, its threads having been coated with ruberine, is screwed into place. A rubber packing is pushed over the loading wire into the stuffing box in the fuse can cap, a brass gland is threaded down so that it is close against the rubber packing, and the follower is screwed home with moderate pressure. The lower tube is screwed into place, compressing a lead washer between it and the fuse can cap. The threads of the follower and lower tube are coated with ruberine. The loading wire is drawn through a lead washer and the hole in the plug proper, and the latter screwed hard against the lower tube.